Increasing xp gained by dps classes in leveling dungeons

[Cabalabob]

The problem is, this would make tanks and healers even less desirable, which in turn would make dps queues even longer, why should I have to run 2 dungeons as a tank or healer to get the same exp a dps gets from 1? Maybe I'll just play a dps instead? Sure I get longer queue times but the exp is the same, so I'm getting rewarded for putting in less effort?

Maybe instead of just outright awarding dps for doing nothing, they could add a queue time exp bonus, so for every 15 mins you spend in queue you get a 25% exp bonus in the content you're doing, so if you end up with an hour queue you'd be getting double exp. This would basically apply to dps indirectly, but even tanks and healers might get some use out of it in those occasional 15 min queues they get.